神农架大九湖泥炭湿地能量通量及平衡分析

研究大九湖泥炭湿地通量,为准确评估泥炭地生态系统与大气间的物质和能量交换提供基础数据。利用涡度相关系统对神农架大九湖2015年9月～2016年8月的净辐射、显热通量、潜热通量及土壤热通量进行了为期1年的连续观测。结果表明:1)泥炭地全年净辐射为3 146.91MJ/m2,显热通量为931.79MJ/m2,潜热通量为1 762.40MJ/m2,土壤热通量为22.26MJ/m2;能量分配主要以潜热为主,占净辐射的56%。潜热通量为能量散失的主要形式,土壤表现为热汇。2)各能量分量季节变化明显,10月、1月、4月及7月的日变化均以净辐射为基础,呈相似的单峰型曲线变化。3)波文比逐月变化不规律,月平均波文比为0.65、波动在0.34～1.06,年波文比为0.53,全年能量分配潜热通量大于显热通量。4)神农架大九湖泥炭地年能量闭合度为0.86,存在14%的能量不闭合。不闭合的原因可能与下垫面状况、季节变化及平流的影响产生的波动等相关。     

Response of soil constituents to freeze-thaw cycles in wetland soil solution

Soil freeze-thaw cycles in the winter-cold zone can substantially affect soil carbon, nitrogen and phosphorus cycling, and deserve special consideration in wetlands of cold climates. Semi-disturbed soil columns from three natural wetlands (Carex marsh, Carex marshy meadow and Calamagrostis wet grassland) and a soybean field that has been reclaimed from a wetland were exposed to seven freeze-thaw cycles. The freeze-thaw treatments were performed by incubating the soil columns at −10 °C for 1 d and at 5 °C for 7 d. The control columns were incubated at 5 °C for 8 d. After each freeze-thaw cycle, the soil solution was extracted by a solution extractor installed in each soil layer of the soil column, and was analyzed for dissolved organic carbon (DOC), NH₄⁺-N, NO₃⁻-N and total dissolved phosphorus (TDP). The results showed that freeze-thaw cycles could increase DOC, NH₄⁺-N and NO₃⁻-N concentrations in soil solutions, and decrease TDP concentrations. Moreover, the changes of DOC, NH₄⁺-N, NO₃⁻-N and TDP concentrations in soil solutions caused by freeze-thaw cycles were different in various sampling sites and soil layers. The increments of DOC concentrations caused by freeze-thaw cycles were greater in the wetland soil columns than in the soybean field soil columns. The increments of NH₄⁺-N concentrations caused by freeze-thaw cycles decreased with the increase of soil depth. The depth variation in the increments of NO₃⁻-N concentrations caused by freeze-thaw cycles in the wetland soil columns was different from that in the soybean field soil columns. The decrements of TDP concentrations caused by freeze-thaw cycles were greater in columns of Carex marsh and Carex marshy meadow than in columns of Calamagrostis wet grassland and the soybean field. The study results provide information on the timing of nutrient release related to freezing and thawing in natural versus agronomic soils, and have implications for the timing of nutrient application in farm fields in relation to water quality protection.     

Long-term effect of wood and peat ash on the growth of Pinus sylvestris on drained peatland

The effect of ash fertilization on height growth and volume production of Scots pine (Pinus sylvestris L.) was studied on oligotroph peatland in southeast Norway. In the year 1944, plots 15 m × 15 m size were fertilized with 0, 4, 7, and 10 tons ha^?1 of wood or peat ash. The area was treeless, but a satisfactory number of pine seedlings were present. All measurements were confined to the central inner plot, 10 m × 10 m area. Most plots were re-fertilized with 10 tons of wood ash ha^?1 in the year 1993. Wood ash had higher content of nutrients, and generally, it had greater growth enhancement effect than peat ash. When the amount of ash was increased, volume production significantly increased for the age period 38–50 years and the total production at age 50 years. The mean annual increment during the first 50 years was about 6 m³ ha^?1 for the plots applied with 10 tons of ash ha^?1. Trees on plots fertilized with 7 or 10 tons in 1944 and replenished with 10 tons ha^?1 at age 50 years (1993) had a mean annual increment of 14 m³ ha^?1 for the stand age period 51–68 years. Over time some tree roots from control plots and plots fertilized with 4 tons ha^?1 have captured nutrients from richer plots. Such effect is to a smaller extent relevant for treatment 7 tons. It is concluded that the content of mineral nutrients of wood and peat ash makes these ashes well suited as fertilizers on peatland.     

Impeded drainage stimulates extracellular phenol oxidase activity in riparian peat cores

Peat drainage, a common land‐use practice in Europe, has been associated with habitat degradation and increased particulate and dissolved carbon release. In the UK, peatland drain blockage has been encouraged in recent years as a management practice to preserve peatland habitats and to reduce fluvial carbon loss and municipal water discoloration. Drain blockage has, however, been found to increase drain‐water dissolved organic carbon (DOC) concentrations and coloration in the short term. In order to investigate the contribution of changes in extracellular phenol oxidase activity to the increase in water coloration following peatland drain blockage, cores collected from a riparian peatland in North Wales were incubated under impeded drainage conditions. Impeded drainage resulted in the stimulation of peat extracellular phenol oxidase activity and heightened soluble phenolic concentrations, suggesting that changes in extracellular phenol oxidase activity may be a key driver of increases in DOC and water coloration following peatland drain blockage. An increase in peat pH with impeded drainage was also observed that may have contributed to the heightened soluble phenolic concentrations – directly (through effects on solubility) and/or indirectly as a driver of the elevated extracellular phenol oxidase activity.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Early performance of native birch (<Emphasis Type="Italic">Betula</Emphasis> spp.) planted on cutaway peatlands: influence of species,stock types and seedlings size

The poor reputation of birch in Ireland is gradually changing, and the interest shown in it by foresters is growing, as is the recognition of the many advantages that this genus offers, especially from an afforestation and ecosystem development point of view. The potential of native birch species was investigated on industrial cutaway peatlands in the Irish midlands. Field experiments were established to evaluate differences (in terms of survival, growth attributes and form) between B. pendula and B. pubescens, between bare-root and container planting, and between small and medium size seedlings. After five growing seasons, B. pendula was found to be the superior species especially on well drained and shallow peat sites. Bare-root B. pendula will grow faster with reasonable form but containerised birch may be favoured on more difficult sites (with deeper and wetter peat). Larger seedlings performed better, regardless of species. This study demonstrated good growth potential for planted birch on cutaway peatlands and that this species should be integrated in further planting programmes.     

Influence of Different Bryophyte Carpets on Vascular Plant Establishment Around Pools in Restored Peatlands

Vascular plants associated to natural peatland pools do not spontaneously colonize edges of man‐made pools in restored peatlands and have proven to be recalcitrant to the usual restoration techniques. The goal of this study was to evaluate the effect of the species used as a seedbed (Cladopodiella fluitans, Sphagnum cuspidatum, or Sphagnum magellanicum) and its developmental stage (established carpet or newly reintroduced fragments) on establishment success in the field of the seeds of four vascular species: Carex limosa, Carex magellanica, Carex oligosperma, and Scheuchzeria palustris. The germination rate was measured after one season and growth after two seasons. Seedbed composition and developmental stage had no effect on Carex, whereas the germination of S. palustris was higher on S. cuspidatum. Growth of vascular plants was slightly improved on S. magellanicum carpets and was lower on seedbeds of C. fluitans. Our results lead us to recommend seeding at the same time as bryophyte fragments are spread and fostering introduction of Sphagnum mosses, preferably to C. fluitans, around artificial pool edges. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of seasonal rainfall and water table movement on the soil solution composition of tropical peatland

ABSTRACT

Understanding the composition of the soil solution of tropical peatlands is important because it directly affects nutrient availability and environmental degradation. The objectives of this study were to investigate temporal fluctuations in the soil solution composition in tropical peatlands in West Kalimantan and Riau, Indonesia and identify the factors controlling these fluctuations. In each site, we established four study plots consisting of three plots under oil palm (Elaeis guineensis Jacq.) plantation and one plot under uncultivated land as the control. Triplicate soil solution samples were collected at 50 and 200 cm depths, fortnightly. During the drought, the pH at 50 cm was low (3.7–4.0), which was influenced by oxidation reactions such as organic acids and NO₃^? generations. The pH at a depth of 200 cm was high (5.9–6.8), due to reduction reactions such as denitrification. High cation concentrations at both depths would result from organic matter decomposition and the limited downward movement of water. Rewetting the West Kalimantan peatland caused a sharp decrease in pH and ionic concentrations at 50 and 200 cm depths, because of the transportation of ions from the upper acidified layer. However, the lower rainfall levels in Riau than West Kalimantan resulted in a gradual decrease in pH and Ca²⁺ concentration. The higher pH levels and ion concentrations in West Kalimantan than in Riau would be influenced by the enhanced microbial activity due to water supply from the risen water table in this site. This study showed that seasonal rainfall and water table movement were the main factors controlling the fluctuations in the chemical composition of soil solutions.     

The impact of climate,drainage and fertilization on the survival and growth of pinus sylvestris L. in afforestation of open,low‐production peatlands

The objective of this study was to analyse the conditions for forest production on open, low‐production peatlands in Sweden with respect to climate, and water and nutrient regimes. The study focused on survival and growth of Scots pine (Pinus sylvestris L.) seedlings, planted 18 yrs ago in five experimental areas evenly distributed between south and north Sweden. Different ditch spacing and NPK fertilizer treatments were combined systematically in all experiments. Survival was positively correlated with temperature sum, fertilization and drainage intensity. Tree growth was not influenced by variations in temperature sum after merely draining, but in combination with fertilization, growth was strongly correlated with climate. In the southern experiments, fertilization increased stand growth eight to nine times, whereas stands on the northern sites did not respond to fertilization. The most important fertilizer element was P. The application of N had no effect on growth. More intensive drainage increased stand growth by 60%. In the southern areas, height development in the most intensive drainage and fertilizer treatments indicates a mean annual increment of 6–7 m³ ha^?1, and no sign of decline in growth was seen. Turf‐planting had positive effects on both survival and growth, especially in less intensively drained plots. A large proportion of damaged trees was observed in the experiment. The frequency of damaged trees was positively correlated with treatment intensity but negatively correlated with temperature sum. The results show clearly that merely draining is not sufficient for successful afforestation of low‐production peatland sites. Fertilization by P and K is a necessary prerequisite, but the effect of fertilization varies with climatic conditions, probably owing to the amount of plant‐available N.